1. Field of the Invention
The present invention relates to a trenched MOSFET structure with a trench termination and the method for manufacturing thereof, and more particularly to a structure of a trenched MOSFET which is suitable for high cell density and can improve the device ruggedness.
2. The Prior Arts
In the structure of a trench Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) or vertical transistor, the gate of the transistor is formed in a trench on top of a substrate and the source/drain regions are formed on both sides of the gate. This type of vertical transistor allows high current to pass through and channel to be turned on/off at a low voltage.
Referring to FIG. 1, a cross-sectional diagram of the structure of a trenched MOSFET is shown. In the prior art, the trench MOSFET has a MOSFET structure comprises a drain region 101, a N-type doping epi layer region 102, a plurality of gate trenches 103, a margin terminating gate trench 104, a gate oxide layer 105, a plurality of channel regions 106, a plurality of source regions 108, a insulating layer 110, a plurality of contact plugs 112, and a metal layer 113. The metal layer 113 is formed on the top of the MOSFET structure for the source metal and the gate and field plate metal of the MOSFET. The gate trenches 103 are covered the gate oxide layer 105 and are defined as the gate of the MOSFET. The insulating layer 110 is formed between the metal layer 113 and the gate trenches 103 for insulating, and the contact plugs 112 are penetrated through the insulating layer 110 and contacted with the metal layer 113.
In the related prior arts, the device structure is achieved with P body formation prior to trench etch, which is not suitable for high cell density with pitch smaller than 2.4 μm. When cell density increases, more trench openings, causes more boron segregation in P body from channel region near by trench during Sacrificial and gate oxidations, resulting in serious punch-through issue. Besides, separation of gate and field plate metal makes longer termination.
The present invention provides a new structure of trenched MOSFET structure with a trench termination around the contacted trenched gate which improves the lack of the prior art.